a) Field of the Invention
The present invention relates to a fluid bearing mechanism for antifriction between a piston and a cylinder of a reciprocating compressor or the like, particularly to a one-way valve for providing or interrupting the communication between the inside and the outside of a compression chamber for use with such compressor.
b) Prior Art
Conventional fluid bearing mechanisms are illustrated in FIGS. 6 to 8. The fluid bearing mechanism comprises: a cylinder 101, a reciprocating piston 102 inserted into the cylinder 101 with a slight clearance G provided therebetween; a hollow interior 102a formed inside the piston 102; a one-way valve 103 provided at a distal end of the piston 102, said one-way valve 103 providing the communication between a space 101a within the cylinder 101 and the hollow interior 102a; and small holes defined through a side surface 102b of the piston 102, said small holes 104 providing the communication between the clearance G and the hollow interior 102a. For the above-mentioned one-way valve 103, U.S. Pat. No. 5,461,859, for example, discloses a structure of one of conventional one-way valves for that purpose.
The conventional one-way valve 103 comprises a valve base 105, a reed 106, a reed retainer 107, and a fastening screw 108 as illustrated in FIG. 8. The valve base 105 is formed with a communication hole 109 which provides the communication between the space 101a within the cylinder and the hollow interior 102a when it is mounted to the piston 102, while the reed 106 and the reed retainer 107 are fixed by the fastening screw 108 in the vicinity of an opening 109a of the communication hole 109 located adjacent to the hollow interior 102a. 
In a state where the piston 102 is stationary, the reed 106 is allowed to close the opening 109a by abutting against an abutting surface 105a around the opening 109a. During the advance trip of the piston 102 within the cylinder 101, pressure difference between the space 101a within the cylinder 101 and the hollow interior 102a urges a gas inside the space 101a to pass through the commutation hole 109 to bend the reed 106, flowing through the opening 109a into the hollow interior 102a, and then flowing out of the small holes 104 into the clearance G. At this moment, excessive bending of the reed 106 is prevented due to the aforesaid reed retainer 107. Thus, the gas flowing out into the clearance G provides the antifriction between the cylinder 101 and the piston 102. On the other hand, during the return trip of the piston 102 within the cylinder 101, the pressure difference between the space 101a within the cylinder and the hollow interior 102a as well as the restoring force by the reed 106 allow the opening 109a to be closed by the reed 106. In this way, the gas inside the space 101a within the cylinder flows in one direction only.
According to the conventional one-way valve 103 of the fluid bearing mechanism, however, it was imperative to process the respective surfaces of the reed 106 and the abutting surface 105a smoothly and accurately enough to prevent the gas from flowing backwardly from between the reed 106 and the abutting surface 105a. Further, as the reed 106 is made from a thin metal plate in order to bend it at a high speed, there has been a problem that it is likely to be deformed at the time of processing or mounting process.
To eliminate the above problems, it is a main object of the invention to provide a fluid bearing mechanism using a one-way valve, which is structured so simply that high processing accuracy is not required, and which is at the same time easy to assemble, with high reliability.
To attain the above objects, there is provided from a first aspect of the invention, a fluid bearing mechanism which comprises: a cylinder; a piston positioned inside the cylinder, having a side surface, end faces and a hollow interior formed therein side, said piston including small holes defined through the side surface for communicating the hollow interior with an exterior thereof; a one-way valve provided between the end face and the hollow interior of said piston, said one-way valve allowing a gas to flow in one direction only, wherein said one-way valve comprises: a cylindrical body provided in parallel with an axial direction of said piston; an abutting portion provided along an inner periphery of said cylindrical body, said abutting portion protruding inwardly, formed with a small communication hole in a substantial center thereof; a moveable element which is moveable inside said cylindrical body in an axial direction thereof; and a retaining body for retaining said moveable element between said abutting portion and itself inside said cylindrical body, said retaining body including a ventilation groove for communicating an inside with an outside of said cylindrical body
According to the first aspect of the invention, when the piston is moved to the compressing direction inside the cylinder, the moveable element is urged toward the inside of the piston, due to the inner pressure of the cylinder and its inertia, so that the small communication hole is opened, thus allowing the gas inside the cylinder to flow from the small communication hole of the one-way valve, through the ventilation grooves into the hollow interior of the piston, and then to flow through the small holes into the clearance between the piston and the cylinder. As a result, the clearance between the piston and the cylinder is insured to keep them away from each other. Further, when the piston inside the cylinder is moved to the expanding direction, the moveable element is reversely shifted toward the outside of the piston so that the small communication hole is closed, whereby the gas is prevented from flowing out into the cylinder, through the hollow interior of the piston and the clearance between the piston and the cylinder.
According to a second aspect of the invention, there is provided a fluid bearing mechanism according to the first aspect, wherein the retaining body is made of an elastic material so that the abutting portion, moveable element and retaining body are allowed to abut to each other at least when the piston is in a stationary state. Thus, when the piston is in a stationary state, the moveable element abuts to the abutting portion to close the small communication hole, while if the piston is shifted toward the compressing direction, the retaining body is elastically deformed due to the force applied to the moveable element, so that the moveable element is moved toward the inside of the piston to thereby open the small communication hole.
According to a third aspect of the invention, there is provided a fluid bearing mechanism according to one of the foregoing aspects, wherein at least the surface of either the moveable element or the abutting portion is made of an elastic material. Thus, when the abutting portion abuts to the moveable element, either the moveable element or the abutting portion is elastically deformed so that not only are they contacted by each other more closely but also the impact developed when they comes into collision with each other is absorbed.
According to a fourth aspect of the invention, there is provided a fluid bearing mechanism according to the first or the second aspect, wherein an abutting surface of said abutting portion is formed concavely conical while an abutting surface of said moveable element opposing to said abutting portion is formed convexly conical with an apex angle of the former being substantially equal to that of the latter. Thus, when they abut to each other, they are contacted by each other over an entire surface thereof, thereby preventing the leakage of gas from the small communication hole.
According to a further aspect of the invention, there is provided a fluid bearing mechanism, which comprises: a cylinder; a piston positioned inside the cylinder, having a side surface, end faces and a hollow interior formed therein side, said piston including small holes defined through the side surface for communicating the hollow interior with an exterior thereof; a one-way valve provided between the end face and the hollow interior of said piston, said one-way valve allowing a gas to flow in one direction only, wherein said one-way valve comprises: a cylindrical body provided in parallel with an axial direction of said piston; an abutting portion provided along an inner periphery of said cylindrical body, said abutting portion protruding inwardly, formed with a small communication hole in a substantial center thereof; and a plug body made of an elastic material, said plug body having a proximal end fixed to an aperture of said cylindrical body, including a ventilation groove for communicating an inside with an outside of said cylindrical body, and a distal end which is able to plug said small communication hole by abutting to said abutting portion.
Accordingly, when the piston is moved to the compressing direction inside the cylinder, the plug body is elastically deformed due to the inner pressure of the cylinder and its inertia, so that the small communication hole is opened, thus allowing the gas inside the cylinder to flow from the small communication hole of the one-way valve, through the ventilation groove into the hollow interior of the piston, and then to flow through the small holes into the clearance between the piston and the cylinder. As a result, the clearance between the piston and the cylinder is maintained to keep them away from each other. On the other hand, when the piston inside the cylinder is moved to the expanding direction, the plug body is restored to its original shape so that the small communication hole is closed, whereby the gas is prevented from flowing out into the cylinder, through the hollow interior of the piston and the clearance between the piston and the cylinder.